Commonly known as "identical
twins" monozygotic twins are from a single egg that has divided after fertilization
to create two embryos. Monozygotic twins consequently share exactly the same genetic
material and are of the same sex.
Monozygotic twins who have been
separated in earliest infancy and raised apart have provided a classic research situation
for social scientists. Monozygotic twins, because their genetic identity, yet different
social experience, makes it possible to disentangle the separate effects of heredity and
Research on monozygotic twins is
essential because the ban on human cloning in many countries worldwide is founded on an
assumption that cloned children will be identical to each other and to their nuclear
How identical would cloned
children be? An understanding essential to the ethical debate - RG Edwards and HK
Beard, Human Reproduction Journals - This paper explores the scientific basis for
this assumption, considering both the principles and practice of cloning in animals and
comparing genetic and epigenetic variation in potential human clones with that in
Cognitive and Personality
Differences Between Identical Twins Following Skull Fractures - Michael J. Lyons and
Adam P. Matheny, The University of North Carolina at Charlotte, University of Louisville
School of Medicine, Journal of Pediatric Psychology 9(4) pp. 485-494, 1984.
The classical co-twin control method was used to evaluate the effects of age at the time
of skull fracture on behavioral functioning several years later. The sample consisted of
13 pairs of male monozygotic twins.
Female Monozygotic Twins with
Selective Mutism - A Case Report.
Journal of Developmental & Behavioral Pediatrics. 27(2):129-133, April 2006. -
SHARKEY, L; MC NICHOLAS, F.
This case report describes a case of young female monozygotic twins who presented with
selective mutism and their treatment spanning a 2-year period. It highlights the strong
genetic association along with environmental factors such as social isolation and
consequences of maternal social phobia, all contributing to treatment resistance, despite
an intensive multimodal biopsychosocial approach. General issues related to the
difficulties in treating monozygotic twins are also addressed.
Monozygotic twins discordant for major depression: a preliminary exploration of the role
of environmental experiences in the aetiology and course of illness. - KENNETH S. KENDLER
and CHARLES O. GARDNER
Background. Genetic effects upon behaviour are pervasive. To what extent are the many
correlates of major depression (MD) due to individual-specific environmental experiences
versus genetic factors correlated with risk for MD?
Methods. From a population-based twin registry, we identified 72 female monozygotic twin
pairs discordant for a lifetime history of MD and compared the affected and unaffected
members on a wide range of putative correlates of MD.
Environmental factors cause pervasive differences in monozygotic twins discordant for MD,
especially in the areas of interpersonal difficulties, psychopathology, social problems